This invention relates to elevating apparatus subject to the repeated operation of rapidly lifting a large retractile mass, it being a general object of this invention to levitate the mass so that elevating the mass is subject mainly to its inertia only, the gravitational effect on the mass being counterbalanced, and to facilitate moving the mass automatically to raise or lower the same as may be required.
Heretofore, it has been common practice to counterbalance structures and various mechanical apparatus such as elevators, cranes draw-bridges, barrier gates and the like, with springs and weights of equal and often greater mass, depending upon the leverage employed. This increased in mass is a great disadvantage when considering the use of space, the cost of augmenting the apparatus, and its operation and most important: its inherently retarded acceleration capability. Accordingly, it is an object of this invention to minimize the increase mass associated with a counterbalanced member that is adapted to be rapidly elevated.
The lifting of a mass is accomplished in various ways, among which is block and tackle or the equivalent cable lift as used in a passenger elevator, or a lever system, or a hydraulic ram system etc. A preferred lifting means as it is disclosed herein is a pneumatic cylinder and piston and compressed air supply system, whereby stored energy is made available for repeated cycles of operation in the event of a power supply failure, and a system that is readily recharged and adapted to rapid operation. It is an object of this invention to implement a pneumatic lift means in combination with a fluid-pneumatic and preferably a hydro-pneumatic mass counterbalancing means that counteracts gravitational forces on the mass, whereby inertia and friction only are involved.
The fluid-pneumatic or hydro-pneumatic mass lifting system herein disclosed has its advantageous application in trafficway barriers installed at points of vehicle ingress into highly sensitive areas of the Government and Military etc. For example, a typical barrier member that is required to be lifted from road level to a height of approximately three feet, must do so within one second (normally 4 to 6 seconds). Also a usual requirement is that the system must complete multiple cycles of operation without the application of outside power. A usual barrier member has a mass of about 6000 lbs. and requires about 180,000 inch lbs. of torque for satisfactory acceleration. It will be seen therefore, that it is extremely advantageous to minimize any additional mass such as a counterbalance attached to moving members of the mass to be accelerated upwardly. It is therefore a primary object of this invention to provide counterbalancing means in the form of a pneumatic spring that is adjustable to counteract gravitational force on the mass, whereby inertia and friction thereof is all that remains to be overcome when accelerating the mass upwardly or vertically.
It is an object of this invention to provide a counterbalancing system, especially adapted to a trafficway barrier mass, and a system that is automatic in its ability to either lift or lower the barrier mass, as circumstances may require. As will be described, there is an adjustable force exerting means for selectively opposing gravitational force on the mass, and adjustment to exact equilibrium is one possible condition that can be attained. However, it may be required that the mass be either automatically lowered or raised in the event of a power failure or like emergency. The condition of equilibrium requires applying a lifting force equal to weight of the mass, in which case the mass is said to be floating. When in a floating condition, the up or down positions are maintained in one of two ways, either by lifting means operation or by a releasable latch means; the lifting means operating to apply lift pressure, or the latch to apply a positive lock. By one fluid pressure adjustment to the force exerting means, a sinking condition is established for automatic closing down of the barrier mass, such as in the event of lifting means failure or when the up position latch is released. By another fluid pressure adjustment to the force exerting means, a lifting condition is established for automatic raising up of the barrier: mass, again such as in the event of lifting means failure or when the down position latch is released.